Internal combustion engine ignition system and tachometer



N 0 I T T. w IR $5 NE9 RIMl E NH TE 9 R A2 Aw TIDE. Q HMM EU mm an C YFLS A N R E T N I Aug. 11, 1964 I INVENTOR. Ralph E. Tarfer BY (1 I Q. W

His Alforney United States Patent 3,144,012 INTERNAL COMBUSTION ENGINEIGNITION SYSTEM AND TACHOMETER Ralph E. Tarter, Chesterfield, Ind.,assignor to General Motors Corporation, Detroit, Mich, a corporation ofDelaware Filed Aug. 29, 1962, Ser. No. 220,277 5 Claims. (Cl. 123-148)This invention relates to a combined ignition system and tachometer forinternal combustion engines which is capable of controlling the ignitiontiming of the engine and indicating the speed of rotation of the crankshaft of the engine.

One of the objects of this invention is to provide a combined ignitiontimer and tachometer which is comprised of static circuit components andwhich includes an ignition control unit and a tachometer unit both ofwhich are controlled by a control unit that has a voltage output whichis a function of engine crank shaft position and speed of rotation.

Still another object of' this invention is to provide a combinedignition system and tachometer for an internal combustion engine whereinthe output voltage of a magnetic pick-up is fed to an ignition controlunit and to a tachometer unit.

A further object of this inventionis to provide a combined ignitionsystem and tachometer for an internal combustion engine wherein abreakerless control unit is operative to control a transistorizedignition unit and a tachometer unit.

Further objects and advantages of the present inven- 'tion will beapparent from the following description, reference being had to theaccompanying drawings wherein preferred embodiments of the presentinvention are clearly shown.

In the drawing:

The single figure drawing. is a schematic circuit diagram of a combinedignition system and tachometer made in accordance with this invention.

. Referring now to the drawing, the reference numeral designates avoltage generating magnetic pick-up device which includes a magneticcore 12 having pole faces 14 and 16. A permanent magnet 18 is providedfor forcing magnetic fiux through the magnetic core 12 and it is seenthat a pick-up coil 20 is wound on one leg of the magnetic core 12.

The magnetic pick-up 10 includes a rotor 22 which is formed of magneticmaterial and which has four radially extending teeth which can swinginto alignment with the 3,144,012 Patented Aug. 11, 1964 a transistorcontrol unit 28 for controlling the ignition timing of the engine 24.The tachometer unit 26 includes a DC. volt meter 30 which is connectedwith conductors 32 and 34. A capacitor 36 is connected across theconductors 32 and 34 and it is seen that the conductor 32 is connectedwith one side of the pick-up coil 20 at junction 38. The conductor 34 isconnected to one side of a diode 40, the opposite side of this diodebeing connected pole faces 14 and 16 as the rotor 22 rotates. The rotorH 22 is driven by the crankshaft of an internal combustion engine 24through a suitable drive line and its rotative position with respect topole faces 14 and 16 beats a definite relationshipto crankshaftposition.

As the rotor 22 rotates, an AC. voltage is induced in the coil winding20. Thus as the radially extending teeth are swinging into alignmentwith the'pole faces 14 and 16, a pulse of voltage is generated of onepolarity and as the radially extending teeth then move out of. alignmentwith the'pole faces 14 and 16, a voltage of an opposite polarity isproduced.

It will be appreciated that the voltage generating magnetic pick-up 10is shown schematically in the drawing and it could take various shapesand forms. As one example, the actual physical construction of themagnetic pick-up 10 may be as shown in application S.N. 126,406, filedon June 16, 1961, and assigned to the assignee of this invention.

In addition to the magnetic pick-up device 10, the system of thisinvention includes a tachometer unit 26 and with an adjustable resistor42. It is seen that one side of the adjustable resistor 42 is connectedwith an opposite side of the pick-up coil 20 at junction 44.

The junctions 38 and 44 are connected with conductors 46 and 48 whichapply an ignition timing control signal to the transistor ignitioncontrol unit 28. The transistor ignition control unit 28 can takevarious forms and in the embodiment shown, it is comprised of' staticcircuit elements. These circuit elements include PNP transistors 50, 52and 54.

The emitter electrode of transistor 50 is connected with a conductor 56which is connected with junction 58. It is seen that the lead wire 56 iscommon to the junction 58 and the lead wire 46 coming from the magneticpickup 10. The junction 58 is connected to one side of an ignitionswitch 60 which is connected to one side of a direct current voltagesource 62 which is the battery in a motor vehicle electrical system. Thebattery 62, of course, is supplied with charging current by a generatorwhich is not shown and when the motor vehicle is running, the voltageappearing between junction 58 and ground in a motor vehicle system isthe output voltage of the generator providing this voltage is higherthan battery voltage.

The collector electrode of transistor 50 is connected to one side of aresistor 64. The opposite side of this resistor is connected to one sideof the primary winding 66 of an ignition transformer generallydesignated by reference numeral 68. The secondary winding 70 of theignition transformer is connected to one side of the primary winding andthis common connection is grounded as shown. The opposite side of thesecondary winding is connected with a rotor contact 72 which rotatesrelative to a distributor cap 74 having fixed electrodes or contacts 76.The fixed contacts or electrodes 76 feed the spark plugs 7 8' on theengine 24 in a manner well known to those skilled in the art. The rotorcontact 72 is driven by the engine 24 and is driven in synchronism withthe rotor 22 of the magnetic pick-up 10. The rotor 72 and distributorcap 74 may be of the type shown in the abovementioned co-pendingapplication, S.N. 126,406.

The emitter electrode of transistor 52 is connected with the baseelectrode of transistor 50 and with a junction 80. A resistor 82 isconnected between junction and the lead wire 56. The collector electrodeof transistor 52 is connected to ground through resistor 84 and isconnected with junction 86. The base electrode of transistor 52 isconnected with the collector electrode of transistor 54 through acapacitor 88. The base electrode of transistor 52 is also connected toground through a resistor A resistor 92 connects the collector electrodeof transistor 54 to ground.

The emitter electrode of transistor 54 is connected with junction 94which is common to lead wires 46 and 56. The base electrode oftransistor 54 is connected with junction 96 and this junction isconnected with conductor 48 coming from the magnetic pick-up 10 and isconnected with junction 86 through a resistor 98.

When the engine 24 is being cranked or when it is running, pulses of AC.voltage are generated in the pickup coil 20 which are indicative ofengine crank shaft position and speed. These pulses are applied acrossthe emitter and base electrodes of transistor 54 to switch this rangedsuch that as the radially extending teeth of the rotor 22 are movingtoward a position where they are aligned with pole faces 14 and 16, avoltage is induced which causes junction 44to be positive and junction38 negative. This applies a reverse bias to the transistor 54 -tomaintain it turned off. In this connection, it is noted that whenignition switch 60 is closed, the positive side of the direct currentsource 62 is also effective to bias the transistor 54 to a turnedcondition since the emitter and base electrodes will have substantiallythe same potential as the positive side of the battery 62.

. The transistor 52 is connected with battery 62 so as to .be biased toconduct in its emitter-collector circuit since there is a base circuitfor this transistor through the resistor 90. Thus, when the ignitionswitch 60 is closed, the emitter of transistor 52 is positive withrespect to the base electrode so that the transistor 52 is conductive inits emitter-collector circuit.

The emitter-collector circuit of transistor 52 forms a .base circuit fortransistor 50. Thus when transistor 52 is turned on in itsemitter-collector circuit, the transistor 50 will likewise be turned onin its emitter-collector circuit so that current can then flow from thepower conductor 56, through transistor 50 and then through the primarywinding 66 of the ignition coil 68. When transistors 52 and 50 areturned on, the capacitor 88 is charged through the emitter to basecircuit of transistor 52 and through the resistor 92.

It was pointed out above that an AC. voltage is in- .duced in thepick-up coil 20 as the rotor 22 rotates. At one point in this cycle, thejunction 38 will be positive with respect to the junction 44. This willapply a forward bias to the transistor 54 to cause it to turn on in itsemitter-collector circuit. When transistor 54 turns on in itsemitter-collector circuit, the capacitor 88 is in etfect connectedbetween the base and emitter-electrodes of transistor 52. The potentialon the capacitor is such as to drive the base electrode of transistor 52positive with respect to its emitter. This causes the transistor 52 toturn off. This substantially opens the base circuit for transistor 50and the transistor 50 will therefore turn off. When transistor 50 turnsoff, a large voltage is induced in the secondary winding 70 which istransferred to one of the spark plugs 78 via the rotor contact 72 andone 'of the fixed distributor cap electrodes 76.

' In summary, it can be seen that when transistor 54 is non-conductive,transistors 52 and 50 are conductive. 'When transistor 54 is conductive,transistors 52 and 50 are turned oif. It is also seen that thetransistor 54 is :turned off when the voltage that is induced in thecoil winding 20 is of such a polarity that junction 38 is negative andjunction 44 positive. Transistor 54 is, of course, biased to conductwhen this potential on the junctions 38 and 44 is reversed. It will alsobe remembered that transistor 54 is biased to its non-conductive stateas the rotor 22 is swinging into a position where it becomes alignedwith pole faces 14 and 16 and is biased to its conductive state as theradial teeth of the rotor 22 are 1:

28 could use NPN transistors rather than PNP transistors and in such anarrangement, the polarities of the applied voltages would have to bereversed. It will also be appreciated that the transistor ignition unitcould take various forms other than that shown in the drawing.

The operation of the electrical tachometer 26 will now be described.When the voltage induced in the pick-up coil 20 is such that junction 44is positive, a current will flow from junction 44, through resistor 42,through diode 40, through the coil of meter 30, and then through leadwire 32 to the junction 38. The polarity of this voltage :is such as toturn off the transistor 54 and at the same time cause a current to flowthrough the meter 30. As the voltage which is induced in the coilwinding 20 4. reverses, there is no current flow through the meter 30since the diode 40 blocks any such current flow.

It will be appreciated from the foregoing that the meter 30 is suppliedwith a pulsating DC. current the frequency of which is a function of thespeed of rotation of the rotor 22 and therefore is a function .of crankshaft speed of the engine 24. This meter will indicate an average valueand the meter can be calibrated forexample in revolutions per minute ofthe crank shaft of engine 24. The capacitor 36 is a filter capacitorwhich is connected directly across the meter and the resistor 42 is acalibrating resistor.

From the foregoing, it can be seen that a combined ignition andtachometer has been provided for an internal combustion engine which isformed entirely of static components and which uses'the magnetic pick-up10 as the prime control for both ignition timing and speed indication.

While the embodiments of the present invention as herein disclosed,constitute a preferred form, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. In combination, an internal combustion engine, magnetic pick-up meansincluding a coil winding and rotor means driven by said engine, anignition'coil having a primary winding and a secondary winding, meansconnecting said secondary windingwith a spark plug on said engine, asource of direct current, semiconductor switch means'connected betweensaid source of direct current and said primary winding of. said ignitioncoil for controlling current flow through said primary winding, anelectrical tachometer, and means connecting said pick-up coil with saidelectrical tachometer and with said semiconductor switch means wherebythe output voltage of said pick-up coil controls both the conduction ofsaid semiconductor switch means and said electrical tachometer.

2. The combination according to claim 1 wherein the electricaltachometer unit includes a voltmeter and a diode connected in seriestherewith.

3. In combination, an internal combustion engine, a spark plug for saidengine, an ignition coil having a primary winding and a secondarywinding, a source of direct current, a breakerless ignition unitconnected between said source of direct current and with the primarywinding of said ignition coil for controlling the current flow throughsaid primary winding, magnetic pick-up means having a pick-up coil androtor means driven by said engine, an electrical tachometer unit havinginput conductors connected across said pick-up coil, said electricaltachometer unit including a voltmeter and a diode connected in serieswith said input conductors, and means connecting said pick-up coil witha pair of control terminals of said breakerless ignition unit.

4. In combination, a source of direct current, an ignition coil having aprimary Winding and a secondary winding, a semiconductor having a pairof current carrying terminals and a control terminal, means connectingsaid primary winding and the current carrying terminals of saidsemiconductor in series and across said source of direct current, amagnetic pick-up having an output coil and a rotatable member that isadapted to be driven by an engine, means connecting said output coilwith the control terminal of said semiconductor whereby saidsemiconductor is turned on and oif in accordance with the voltagegenerated in said output coil, and an electrical tachometer connectedwith said output coil to indicate the speed of rotation of saidrotatable member.

5. In combination, a source of direct current, an ignition coil having aprimary winding and a secondary winding, a magneticpick-up. having arotatable member adapted to be driven by an engine and having an output5 coil separate from said ignition coil, a semiconductor ReferencesCited in the file of this patent switch means having a pair of currentcarrying terminals UNITED STATES PATENTS and a control terminal, meansconnecting the current carrying terminals of said semiconductor switchmeans 5 2 5 gg' g and said primary winding of said ignition coil inseries 5 2468696 Westbgr'g A 5 1949 and across said source of directcurrent, means connecting 2:542638 D esch Feb 1951 the control terminalof said semiconductor switch means 2,6493 WargO Aug 1953 with saidoutput coil of said magnetic pick-up, an electri- 2,7909 14 Dingman APL30, 1957 cal tachometer, and a means connecting said electrical 2 929022 carpenter Mar 15 19 0 tachometer with said output coil of saidmagnetic pi kp- 10 3,087,090 Konopa Apr. 23, 1963

1. IN COMBINATION, AN INTERNAL COMBUSTION ENGINE, MAGNETIC PICK-UP MEANSINCLUDING A COIL WINDING AND ROTOR MEANS DRIVEN BY SAID ENGINE, ANIGNITION COIL HAVING A PRIMARY WINDING AND A SECONDARY WINDING, MEANSCONNECTING SAID SECONDARY WINDING WITH A SPARK PLUG ON SAID ENGINE, ASOURCE OF DIRECT CURRENT, SEMICONDUCTOR SWITCH MEANS CONNECTED BETWEENSAID SOURCE OF DIRECT CURRENT AND SAID PRIMARY WINDING OF SAID IGNITIONCOIL FOR CONTROLLING CURRENT FLOW THROUGH SAID PRIMARY WINDING, ANELECTRICAL TACHOMETER, AND MEANS CONNECTING SAID PICK-UP COIL WITH SAIDELECTRICAL TACHOMETER AND WITH SAID SEMICONDUCTOR SWITCH MEANS WHEREBYTHE OUTPUT VOLTAGE OF SAID PICK-UP COIL CONTROLS BOTH THE CONDUCTION OFSAID